1. Field of the Invention
The present invention relates to switching devices which are operated in a swinging manner and more particularly it relates to a switching device which outputs two-position change-over signals with a consecutive pressing operation and which is suitable for use in a drive switch of a car-mounted automatic widow apparatus and the like.
2. Description of the Related Art
FIG. 12 is a sectional view of a known switching device of the above-mentioned type. As shown in the figure, a casing 1 having a bottom wall 1a has first, second, and third stationery contacts 2a, 2b, and 2c fixed therein by insert-molding and has three terminals 8 extending from the corresponding stationery contacts 2a to 2c and protruding downwards from the casing 1. Each of the stationery contacts 2a to 2c is exposed on the bottom wall 1a of the casing 1 and the central stationery contact 2a has a conductive plate 3 swingably disposed thereon, serving as a fulcrum thereof. The conductive plate 3 made from a metal plate and having an approximate M-shape in side view includes a crest portion 3a and a pair of rising portions 3b and 3c at both sides of the crest portion 3a, and the longitudinal two ends of the conductive plate 3 are respectively contactable with the stationery contacts 2b and 2c. The conductive plate 3 has an actuator 4a of a drive body 4 disposed thereon. Since the drive body 4 is constantly urged towards the bottom wall la by a coil spring 5, the actuator 4a lies in elastic contact with the conductive plate 3. The drive body 4 and the coil spring 5 are incorporated into a recess 6a of a turning lever 6. The turning lever 6 is turnably supported by a cover 7 fixed to the casing 1 so as to cover the casing 1, and an operating knob (not shown) is fixed to the turning lever 6. The operating knob is operated in a swinging manner by an operator. When the turning lever 6 is turned in conjunction with the swinging of the operating knob, the actuator 4a of the drive body 4 slides on the conductive plate 3.
FIG. 12 illustrates a non-operational state of the known switching device in which the turning lever 6 is not turned, and the stationery contacts 2a and 2c are electrically connected with each other via the conductive plate 3 while the stationery contacts 2a and 2b remain in a switched-off state. In this state, when the turning lever 6 is turned clockwise in the figure by pressing the operating knob, since the actuator 4a slides on the rising portion 3b while compressing the coil spring 5, the conductive plate 3 turns counterclockwise in the figure upon the actuator 4a passing through the stationery contact 2a. As a result, since the conductive plate 3 is detached from the stationery contact 2c and comes into contact with the stationery contact 2b, the stationery contacts 2a and 2b are electrically connected with each other via the conductive plate 3 and are thus changed to a switched-on state. When the pressing force exerted on the turning lever 6 is removed, since the restoring force of the coil spring 5 causes the actuator 4a to slide on the rising portion 3b in the reverse direction, the conductive plate 3 turns in the reverse direction upon the actuator 4a passing through the stationery contact 2a and returns to the state shown in FIG. 12, and thus the stationery contacts 2a and 2b return automatically to a switched-off state.
Also, in the state shown in FIG. 12, when the turning lever 6 is turned counterclockwise in the figure by pressing the operating knob, although the actuator 4a slides on the rising portion 3a, since the conductive plate 3 has previously been pressed against the stationery contact 2c, it does not turn; hence the stationery contacts 2a and 2b remain in a switched-off state.
When two groups of the stationery contacts 2a to 2c are disposed in two rows on the bottom wall 1a of the casing 1, and the conductive plate 3, the actuator 4a, and the other parts are disposed for each group of the stationery contacts 2a to 2c, two sets of switching elements sharing the casing 1 and the turning lever 6 can be disposed side by side. Accordingly, by disposing these two sets of switching elements so as to be symmetric with respect to a point in plan view, a double-pole double-throw switching device in which, when the operating knob is pressed into one direction, one of the switching elements outputs a first drive signal, and when the operating knob is pressed into the other direction, the other switching element outputs a second drive signal can be achieved.
Such a switching device has been widely used as a drive switch of a car-mounted automatic window apparatus. In this case, since the drive signal for performing an operation of opening or closing a window can be output while the operating knob is being pressed, a manual operation by which the degree of opening of the window can be set as desired can be performed.
The drive switch of a car-mounted automatic window is also required to have an operational function of fully opening or closing the window through one-touch operation. In order to additionally provide such an operational function to the foregoing switching device, the switching device usually has a push-switch (a tactile switch) disposed next thereto, which is operated by pressing in conjunction with the turning of the turning lever 6. Such an example known switching device has a structure in which a pressing drive rod is disposed so as to protrude downwards, passing through the bottom wall 1a of the casing 1, and when the turning lever 6 is turned by a large amount, the pressing drive rod is pressed down so as to actuate the push-button; alternatively, another structure in which a pressing drive body is disposed so as to protrude sidewards from the casing 1, and when the turning lever 6 is turned by a large amount, the pressing drive body actuates the push-button. In such an example known switching device, the operating knob is pressed down so as to turn the turning lever 6 by a predetermined amount and to cause the conductive plate 3 to come into contact with the stationery contact 2b which has been kept away from the conductive plate 3, and then the turning lever 6 is further turned by another predetermined amount by further pressing down the operating knob. With this operation, the pressing drive rod or the pressing drive body is pressed down by the turning lever 6 so as to actuate an operating unit of the push-switch by pressing, so that a drive signal for performing an operation of fully opening or closing the window is output.
In the known switching device shown in FIG. 12, in order for the actuator 4a of the drive body 4 to swing the conductive plate 3, the turning center of the turning lever 6 for driving the drive body 4 must be set away from the conductive plate 3 to a certain extent; hence, the turning lever 6 for storing the drive body 4 and the coil spring 5 is required to have a reasonable size, thereby constituting a limiting factor of reducing the overall size and thickness of the switching device. Accordingly, as described above, when a pressing drive rod or a pressing drive body for actuating a push-switch is additionally disposed in such a switching device, the overall switching device including the pressing drive rod protruding downward or the pressing drive body protruding sidewards becomes considerably large and also its structure becomes complicated.
When the known switching device shown in FIG. 12 is assembled, the drive body 4 incorporated into the recess 6a of the turning lever 6 together with the coil spring 5 must be disposed on the conductive plate 3 in the casing 1; however, since this assembling step must be carefully performed such that the drive body 4 and the coil spring 5 do not drop off from the turning lever 6, the switching device is difficult to assemble. As a result, when a pressing drive rod or a pressing drive body for actuating a push-switch is additionally disposed in such a switching device, the switching device becomes more difficult to assemble, thereby leading to a reduced productivity.